My blood pressure dropped 1000% percent when I stopped doing ranked matches. It seemed to love matching me with people over in France, which resulted in some rather unplayable matches.
It pretty much goes by streak - I think. For me I'd always go 37, 47, 57, 67, 77, etc till you'd lose. If you fight someone ranked higher than you, you get a random amount of points. Now, as for determining the amount of points you'd lose - that's a black voodoo magic I haven't the foggiest idea of how it works. I'm going to roll with "It's RNG"
Oh, side note - disconnects cost you 300 points. I know this because the glorious Ranked match finder would match me with like, 4 people at once, get confused as shit, and disconnected me from all of them, crashing my xbox and costing me 300 points for each disconnect.
That, and I may/may not have quit after some rather disappointing loses. >_>